648 is a reasonably clear channel, but I think there's some disappointment in certain quarters. Most of the output will come from their Kent facility rather than the Ross itself. Hopefully the monthly use of Manx Radio's 20Kw 1368 tx will continue, it's very popular and gets out well.
I think that lovely ampliphase machine on board the Ross has sung it's last song sadly, I don't think they even have working generator capacity for it anymore

On the Caroline website under AM plans it says 1 KW ERP has been allocated on 648 KHZ.

OFCOM said 1kW ERP, then realised just what coverage was possible at that power level with a good aerial - rumour has it that the power level is likely to be reduced.

In the latter days of the Ross Revenge, they seldom ran more than a kilowatt (since they couldn't afford the diesel!) and their coverage from the ship was pretty good. A kilowatt on land will not go anywhere near as far, but could give fairly good daytime coverage in much of South East England with a reasonable antenna. Night time local coverage will be poorer, though they'll get skywave into Europe. 648kHz was a pretty clear frequency when I was at Crowborough and Orfordness, but since the demise of the World Service MW, other countries have jumped on the frequency. As I recall, there's a fairly powerful Italian thing on 648kHz and there was a Danish or Finnish local effort on there too.

Wow, never knew that Albert... that they rarely used more than 1KW toward the end.... just used to hear about this 70KW they had... but I guess that was "available" rather than actually in use right?... as always, interesting stuff Mr H

The Continental ampliphase rigs were astonishingly efficient for AM (for your homework, look up Ampliphase, Cheirix and Doherty modulation). Despite that, they had to conserve diesel, so turned the power down a lot. At times it was almost a choice between running the domestic services or the transmitters!

A friend of mine is writing a history of broadcasting and the depressing part is that all pirates fail eventually!

Surely some failed purely our of the laws being introduced that made them unable to legally get supplies even if upping the anchor and broadcasting outside local waters. The owners deciding to switch-off to stay within the law of the day. This action made them not financially viable businesses.

I'm sure there were some, I can think of Veronica & RNI that would of continued to to make money had the Dutch version of the MOA not been ratified.

Veronica of course went on to gain an FM license in The Netherlands and I believe continue till this day.

RNI was astonishingly successful in its day, and made a lot of money for its owners. Sadly, the ship wasn't suitable for operation further offshore, so the Dutch equivalent of the MOA was the end.

The same applied to Veronica - the ship wasn't suitable for anchoring in deep water - and they'd been offered time on the Dutch national networks, so they opted to come ashore. You're right - they still continue today, but not with the massive mass-market appeal that they once had.

I had a listen to 648kHz over the last few days, and it's a dreadful choice of frequency for a (relatively) low power operation. There's Radio Murski Val from Slovenia (often audible in the Netherlands during the daytime and always at night) and RNE R.Nacional (Extremadura) from Spain which I can hear right now. It's as if they've been deliberately issued a dud frequency to make certain that they can't succeed....

If you tune to 1224kHz you'll hear a signal of about the power that Caroline will be able to use. It's "Radio Universe" from the Netherlands using an experimental Class E PWM rig that peaks at about 1kW. It's perfectly receivable in most of Eastern England during the day, but disappears completely at sunset. It also suffers (a bit) from splatter from the badly controlled modulation of some of the 1215kHz rigs. The modulator could do with a slight tweak - it's peaking at about 90% mod at the moment, and could do with a bit more bass. However, it's not bad for a homebrew rig that cost about €150 to build!

If one were a cynic then it would be easy to believe that Caroline were given a dud however at the end of the day that 1kW EMRP will in the eyes of the regulator be enough to cover their desired coverage area under daytime groundwave conditions.

it is not part of the deal to protect the frequency from night-time skywave interference however while their 'local' coverage may be reduced at night their field strength should be enough for the hardcore Caroline listeners.

On not a dissimilar note back in 2000 I was part owner of a US local AM (WLYC 1050) 1kW day and 30W night both non-directional. The stick was 129' tall so under 90 degrees. The frequency was protected for a New York 50kW station a couple of hundred miles away which, if we turned off the night TX one could hear on skywave however switching on the 60W LPB was enough to put a signal across Williamsport the city of license and over the NY station. However, as Tiff Needell is known to say, "you know me". How could I increase coverage without upsetting the FCC. I swapped the low level mod LPB TX for a Radica AM50 which I took over from the UK. With high level PWM modulation this kicked ass and nearly doubled our coverage due to the greatly increased mod and far better audio quality being that you've done away with any transformers.

I think Caroline will end up using the TRAM 10kW TX at somewhere between 3-5kW due to antenna efficiency to obtain the required EMRP and with a full-size stick and better than average ground system they should do OK for the fruit farmers of Essex & Suffolk.

1584 at Chingford cranks out on his 1kW emrp and he now has a very nice BE 5kW TX which I saw when visiting Surgit's studio in Hayes earlier this year before Chicago built out his new site with the T antenna.

Growing up in NW London,Radio Odyssey were a huge influence on me.
I loved that station!
I recall seeing Radio Odyssey scratched into school desktops!
What area did you broadcast from?
What type of rigs?
And who was involved?

Around the same time, I met the Radio City guys - Bill was really rather an unusual Teddy Boy! Their favoured site in Colindale (within sight of the Police training facility at Hendon!) had a stream running through it, and the used to put their earth rods into the bed of the stream, with an inverted-L hanging from nearby trees. They used a rotary converter to get the HT for their 807 rig. They used to get good signal reports from eastern Europe with that set-up!

A couple of years later, the first of the SMPSU chips became available. These were capable of PWM power control, and it struck me that if you could get one to oscillate in the medium wave band (instead of the 120kHz or so that they normally worked at), it could make the basis of a very efficient medium wave transmitter. The SG1524 cost a few pence, and with a couple of big power transistors (I used 2N3055s), I could develop 15 Watts carrier / 60 Watts peak from two car batteries at the lower end of the medium wave band. I couldn't get the chip to oscillate any higher than 850kHz, unfortunately. This meant that the aerial was long (or inefficient). Still - we ran enough of these rigs to have some of them taken away by a baffled Gotts!

My biggest medium wave effort in those days used four 813s and was modulated with a valved "Vortexian" public address amplifier. I fried two modulation transformers with that set-up, but when it worked well, it sounded amazing. It was the first time I used envelope feedback to linearise the modulation, and the improvement in quality it gave was astonishing.

A subsequent (smaller) series of rigs used this technique to overcome the distortion inherent in screen-grid modulation. The beauty of this approach was that it didn't require a high powered audio amplifier to fully modulate the rig. Some of these were mains powered, and used hum cancellation techniques as well to improve the audio still further. Many of the South London stations used my screen-grid modulated rigs, so you may well have seen my handiwork back then. I used to use a pair of 6146s with around 700V on the anodes, giving (usually) 22 - 24 Watts carrier and around 90 Watts on peaks - if the output match was correct! This little series of rigs was loosely based on the Knight T150 design, but with envelope feedback, very basic audio compression and a power reduction circuit to protect the finals if it was fired into a really bad match. Looking back on the design now, I think that it was pretty sophisticated for pirate use in those days!

They've been allocated a couple of hundred Watts on 648kHz. This will give them reasonable daytime coverage of East Anglia, but will be useless at night.

I beg to differ - they have been allocated (and I am told use) 1kw emrp. Also, I'm pretty sure (but will be gladly proven wrong if you can teach me!) that 1kW emrp is 1kW emrp, regardless how good or bad the antenna - the only difference being the amount of tx power needed to deliver the radiated power out of the antenna! Pretty sure the rig is 2.5kW solid state, but I don't know what power it runs at.

The antenna at Orfordness looks like a bit less than a quarter wave vertical. A ¼-wave would be about 116m high - the original 648 kHz array (that I worked on in the early 80s) had five 105m towers, which were isolated at their bases. Presumably Caroline are using one of those. Their rig is probably running not much more than a kilowatt to get their allocated power output - the antenna should be quite efficient.

648kHz is a dreadful choice of frequency - during the winter they'll only have about 5 hours a day during which they'll have interference-free coverage. I'm convinced that OFCOM has tried to cripple them with this awful frequency. Now that the French (and many other Europeans) have abandoned medium wave, there are plenty of open frequencies that they could use. These days it'll just be a case of telling the EBU which frequency you're going to use!

The Nautel is a nice rig. I've installed plenty of them over the years. They do have a bit of a problem with elevated temperatures in the tropics, but that won't be a problem on the English East Coast! The Marconi antenna should work reasonably OK - it's just that 648 kHz is a really duff frequency.

Right now, I'm just about 12 km LOS from their site (I'm visiting in Suffolk) and a quick check right now at 23:55 shows their kilowatt from just up the road to be completely flattened by Radio Murski Val from Slovenia and RNE R.Nacional (Extremadura) from Spain - if I turn the radio exactly the right way I can hear Spanish, and the eastern European station thrashes in with the radio in any other position. Radio Caroline is in the mush somewhere, wasting the little bit of power they're allowed. It's almost audible at one position of the radio. I might go over to Orfordness tomorrow night, tune to 648 kHz on the car radio, and see how far they're audible. I'd be surprised if it was more than a couple of km!

I'm really tempted to put 100W p-e-p into a "Tower Block Sloper" on 819 kHz and modulate it with Caroline off the 'net. I can guarantee that it would get out better than the mess they're wasting their time with at the moment, and it would be audible in London and East Anglia at night!